C. Aerospace Propulsion and Power

1. Scope

Advanced propulsion and power technologies provide the
muscle for Army land combat systems. Toward this end, the
Army aerospace propulsion and power technology area focuses
on technologies that will result in aircraft and missile
propulsion systems and components, including prime power
transmission, that are more compact, lighter weight, higher
horse power, more fuel efficient, and lower cost than those
currently available. It also focuses on compact, lighter
weight, lower cost, and longer duration aircraft and space
vehicle power generation systems and their components. In
addition, it includes associated fuels and lubricants. It
excludes efforts directed toward generic materials, which are
included in Materials, Processes and Structures, and
moderate- to large-scale manufacturing process development,
which is included in Manufacturing Science and Technology.
Missile propulsion is discussed in Section I, Conventional
Weapons.

2. Rationale

Aerospace propulsion and power technology will provide
mobility for next generation Army aircraft and missiles and
upgrades to current systems. These systems, coupled with
modern doctrine, tactics, and training, will provide our
soldiers the capabilities needed to execute precision
strikes, to dominate maneuver battles, and to project and
sustain combat power.

Army aerospace propulsion and power technology is
developed jointly and in close coordination with the other
military services, the National Aeronautics and Space
Administration (NASA), and industry, thus inherently
promoting dual use technologies and processes. As a result,
both civilian industry and the military industrial base are
strengthened and development is faster, more efficient, and
less costly. In-house Army laboratory expertise is needed to
ensure that those technologies pertinent to Army requirements
are addressed, and to enable the Army to be a smart buyer and
to perform the high risk technical investigations, research,
and development that ensure attainment of Army requirements.
The overall cost to the taxpayer for joint ventures having
both military and civilian applications is therefore
minimized.

3. Technology Subareas

a. Rotorcraft Propulsion

Goals and Time Frames

In the gas turbine area, under the Integrated High
Performance Turbine Engine Technology (IHPTET) program, the
Army, other Services, National Aeronautics and Space
Administration (NASA), Defense Advanced Research Projects
Agency (DARPA), and industry are working together to reduce
specific fuel consumption by 40 percent and to increase the
power-to-weight ratio by 120 percent of future (compared with
current) engines by FY03. This enhanced propulsion capability
will significantly improve Army rotorcraft range and payload
characteristics starting in the year 2000 and beyond. IHPTET
technology will also be applicable for ground vehicles. An
"Advanced Concepts (or IHPTET IV)" activity has
also begun with the goal of defining the path for gas turbine
propulsion technologies and challenges beyond IHPTET Phase
III.

b. Progress and Plans

Gas Turbine Engine Technology

Typically, turbine rotors use the "fir-tree"
method for the blade/disk attachment. However, by employing
an integrally bonded blade /disk rotor, the disk material in
the "dead" rim can be eliminated, significantly
reducing disk weight. Under the Low Inertia Turbine Program,
AlliedSignal has fabricated an integrally bonded rotor
consistent with the JTAGG II /IHPTET Phase II goals (STO
IV.C.1). Design bond strength requirements have been success
fully demonstrated in an 1100 F-spin test. Minor
modifications have been made to improve the bonding process,
and another rotor will be fabricated and spin pit tested in
1Q FY97. This is the attachment configuration for the JTAGG
II HPT which, upon successful completion, will reduce the
risk of incorporating this technology into the gas generator.

Rotorcraft Drive Technology

Spiral-bevel gears (SBGs) are used extensively in
rotorcraft applications to transfer power and motion through
nonparallel shafts. While SBGs have had considerable success
in these applications, they are a major source of vibration
in gearboxes, and thus a main source of cabin noise. An
analytically based optimal design tool was developed which
modifies the gear tooth profile to minimize SBG noise and
vibration. Advanced design spiral-bevel gears were tested,
including configurations with increased fillet radius to
reduce tooth bending stress, modified tooth geometry to
reduce noise, and provisions to reduce premature contact and
eliminate wear problems. In FY96, an optimum design was
fabricated and tested. The test demonstrated more than a 50
percent decrease in gearbox vibration and over 10dB in noise
reduction.

Major Technical Challenges

In order to reduce fuel consumption, turbine engine
thermodynamic efficiency must be in creased. Meeting IHPTET
goals will require cycle temperatures near or equal to
stoichiometric combustion conditions. If the engine
power-to-weight ratio is to be increased, materials must be
found that can survive substantially higher operating
temperatures, approaching 1900°C (3500°F) in the combustor
and turbine, and withstand a 280°C (500°F) increase over
present levels in the compressor while retaining required
mechanical strength. In addition, methodologies must be
developed and validated for the design of more highly loaded
aerodynamic components, allowing lower parts counts. And
drive train research must be performed to lower weight,
volume, noise, and durability barriers. Specific technical
challenges are highlighted below.

In the fuels and lubricants sub-subarea,
the Army's major thrust is in the development and
demonstration of new analytical technologies by 1997 for
rapid assessment of petroleum quality using spectroscopic and
chromatographic methods. The technology being developed will
be incorporated into the Army's new Petroleum Quality
Analysis system.

Major Technical Challenges

The new analytical methods will enable a
significant reduction in the operational requirements for
petroleum testing in the field (i.e., 50 percent less
manpower, 70 percent reduced testing time, and 60 percent
less test hardware). The technical challenges encompass
compressing the testing time, developing improved detection
systems, correlating testing results, and developing expert
systems.

4. Roadmap of Technology Objectives

The roadmap of technology objectives for
Aerospace Propulsion and Power is shown in Table IV-C-1,
below.